Julian Assange, who is awaiting a verdict on whether he shold be deported to Sweden to face allegations of rape and sexual assault. Photograph: Dan Kitwood/Getty Images

The supreme court will deliver its verdict next Wednesday on whether or not the WikiLeaks founder, Julian Assange, should be deported to Sweden to face allegations of rape and sexual assault.

The short judgment on 30 May will include an explanation of the decision the seven-strong panel of justices reaches. It is expected to focus on the narrow issue of whether or not a European arrest warrant (EAW) issued by a prosecutor is valid.

EU treaty provisions governing extradition specify that a warrant must be drawn up by "competent judicial authorities". Lawyers for Assange argue that a prosecutor is not a judge or a "judicial" official.

Clare Montgomery QC, for the Swedish authorities, maintained that the arrest warrant was valid because judicial authorities, at least in the preliminary stages of investigations where arrest is being sought, need not be independent and impartial.

If the supreme court blocks the Swedish extradition request it will throw the EAW system into turmoil and have significant implications for other extradition cases within Europe.

The seven justices who heard the appeal are Lord Phillips, Lord Walker, Lady Hale, Lord Brown, Lord Mance, Lord Kerr and Lord Dyson. The fact that so many judges are considering the case suggests that they recognise it is a particularly complex and significant issue. The two-day appeal hearing was held at the beginning of February.

Assange denies the allegations against him.

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